JP2014134126A - Solenoid valve Drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve energy efficiency of a solenoid valve drive device.SOLUTION: A solenoid drive device includes: charging means for charging a capacitor so that a charging voltage of the capacitor is equal to a predetermined voltage higher than a power supply voltage; a discharge switch provided upstream of a coil of a solenoid valve in a current-carrying path for carrying a current to the coil, the capacitor being connected to the discharge switch; and peak-current supply means for carrying a peak current to the coil for promptly actuating a valve element of the solenoid valve by discharging electric energy from the capacitor to the coil by turning on the discharge switch. The peak-current supply means turns on/off the discharge switch so that the current flowing to the coil reaches a target maximum value Ip of the peak current when target time Tp passes since start of driving the solenoid valve. It is thereby possible to set a peak current period until the coil current is equal to the target maximum value Ip to the target time Tp, and to prevent loss of electric energy due to the too short peak current period.

Description

  The present invention relates to a device for driving a solenoid valve, and more particularly, to a solenoid valve drive device that discharges high voltage energy charged in a capacitor to a coil of a solenoid valve to improve the operation responsiveness of the solenoid valve. .

For example, as a fuel injection valve (injector) for injecting fuel into each cylinder of an internal combustion engine, an electromagnetic valve is used in which a valve element is lifted and opened by energization of a coil.
Such a solenoid valve driving device includes a booster circuit that generates a voltage higher than the power supply voltage and charges the capacitor, and a discharge switch that connects the capacitor upstream of the coil of the solenoid valve. is there.

  In this type of solenoid valve drive device, the peak current for quickly moving (lifting) the valve body of the solenoid valve by turning on the discharge switch and discharging the capacitor to the coil at the initial stage of the solenoid valve drive period. Flow through the coil. When the current flowing through the coil (hereinafter also referred to as coil current) reaches the target maximum value (peak value) of the peak current, the discharge switch is turned off, and thereafter, the power supply voltage is applied to the coil until the driving period ends. A constant current is passed to keep the solenoid valve open (see, for example, Patent Document 1).

JP 2006-152987 A

  In the conventional solenoid valve driving device, the discharge switch is kept on until the coil current reaches the target maximum value from the start of driving of the solenoid valve. For this reason, the period from the start of driving of the solenoid valve to the coil current reaching the target maximum value (hereinafter referred to as peak current period) becomes shorter as the voltage of the capacitor (hereinafter also referred to as capacitor voltage) increases.

  Here, if the peak current period becomes too short, the moving speed of the valve body of the solenoid valve does not increase as expected. This is because it is difficult to move a heavy object at a stroke, and this tendency becomes more prominent as the mass of the valve body increases. If the peak current period is too short, the magnetic force generated by the peak current is not sufficiently used for the lift movement of the valve body and is converted into heat inside the solenoid valve. The loss of will increase. Such a loss is called a loss in the initial stage of driving.

  For this reason, if the peak current period becomes too short, the capacitor needs to store extra energy for the initial driving loss in addition to the energy used to lift the valve body of the solenoid valve. Therefore, a capacitor having a large electrostatic capacity is required.

  In particular, the electric energy of the capacitor is also used to drive an electric load (for example, an electromagnetic valve for other uses) different from the electromagnetic valve to be driven, and the voltage V1 necessary for driving the electric load is driven. When the voltage is higher than the optimum voltage V2 for driving the target solenoid valve, the capacitor voltage is set to the higher voltage V1 of the voltage V1 and the voltage V2. In that case, with respect to the solenoid valve to be driven, the capacitor voltage becomes higher than the optimum voltage V1, so that the peak current period becomes too short and the loss at the initial stage of driving becomes large.

  Therefore, an object of the present invention is to provide an electromagnetic valve driving device that can improve energy efficiency.

  The electromagnetic valve driving device of the present invention includes a charging means for charging the capacitor so that a charging voltage of the capacitor becomes a predetermined voltage higher than a power supply voltage, and the coil in an energization path for flowing current to the coil of the electromagnetic valve. Discharge switch for connecting the capacitor to the upstream side, and a peak current for turning on the discharge switch and discharging the capacitor from the capacitor to the coil to cause the peak current to quickly move the valve body of the solenoid valve to the coil Supply means.

  Then, the peak current supply means turns on / off the discharge switch so that the current flowing through the coil (coil current) reaches the target maximum value of the peak current when the target time has elapsed from the start of driving of the solenoid valve. .

  For this reason, the peak current period from the start of driving of the solenoid valve until the coil current reaches the target maximum value can be set as the target time, and the loss of electric energy due to the peak current period being too short (the driving described above) Initial loss) can be prevented. Therefore, energy efficiency can be improved.

It is a block diagram which shows the fuel-injection control apparatus of embodiment. It is explanatory drawing explaining operation | movement of a drive control circuit. It is explanatory drawing explaining the operation | movement of a drive control circuit, and the effect | action of a fuel-injection control apparatus. It is explanatory drawing explaining the reason for turning on / off a discharge switch. It is a flowchart showing the initial setting process which a microcomputer performs. It is a flowchart showing the peak current supply process which a drive control circuit performs.

  Hereinafter, a fuel injection control device according to an embodiment to which an electromagnetic valve driving device of the present invention is applied will be described with reference to the drawings. The fuel injection control device according to the present embodiment includes four electromagnetic solenoid injectors that supply fuel to each cylinder # 1 to # 4 of a multi-cylinder (4 cylinders in this example) diesel engine mounted on a vehicle. (Hereinafter referred to as electromagnetic valves), and by controlling the energization start timing and energization time to the coils of each solenoid valve, the fuel injection timing and fuel injection amount to each cylinder # 1 to # 4 are controlled. Control. In this embodiment, the switching element used as a switch is, for example, a MOSFET, but may be another type of switching element such as a bipolar transistor or IGBT (insulated gate bipolar transistor).

  As shown in FIG. 1, in the fuel injection control device 31, a terminal CM to which one end (upstream side) of a coil 41a of a solenoid valve 41 to be driven is connected and the other end (downstream side) of the coil 41a are connected. Terminal INJ, a cylinder selection switch T10 which is a switching element having one output terminal connected to terminal INJ, and a current detection resistor connected between the other output terminal of cylinder selection switch T10 and the ground line. R10.

  The solenoid valve 41 is a normally closed solenoid valve. In the solenoid valve 41, when the coil 41a is energized, a valve body (not-shown nozzle needle) (not shown) moves to the valve opening position (in other words, lifts), and fuel injection is performed. When the energization of the coil 41a is interrupted, the valve body returns to the original valve closing position, and fuel injection is stopped.

  FIG. 1 shows only one solenoid valve 41 corresponding to the nth cylinder #n (n is any one of 1 to 4) out of the four solenoid valves 41. The driving of the electromagnetic valve 41 will be described. Actually, the terminal CM is a common terminal for the solenoid valve 41 of each cylinder, and the coil 41a of each solenoid valve 41 is connected to the terminal CM. The terminal INJ and the cylinder selection switch T10 are provided for each electromagnetic valve 41 (in other words, for each cylinder). The cylinder selection switch T10 is a switching element for selecting the electromagnetic valve 41 to be driven (in other words, the cylinder to be injected).

  Further, the fuel injection control device 31 includes a constant current switch T11 that is a switching element having one output terminal connected to a power supply line Lp to which a vehicle battery voltage (battery voltage) VB as a power supply voltage is supplied, and a constant current. An anode is connected to the other output terminal of the switch T11, a cathode D11 having a cathode connected to the terminal CM, and a current return diode having an anode connected to the ground line and a cathode connected to the terminal CM. A diode D12 and a booster circuit 33 are provided.

The diode D12 causes a current to flow back to the coil 41a when the constant current switch T11 is turned off from on while the cylinder selection switch T10 is turned on.
The booster circuit 33 includes a capacitor C0, an inductor L0, a booster switch T0 that is a switching element, a backflow prevention diode D0, a current detection resistor R0, and a charge control circuit 35 that drives the booster switch T0. Prepare.

  The capacitor C0 accumulates electric energy for causing the coil 41a to flow a peak current for quickly moving (lifting) the valve body of the electromagnetic valve 41 in the valve opening direction. The inductor L0 has one end connected to the power supply line Lp and the other end connected to one output terminal of the boost switch T0. The resistor R0 is connected between the other output terminal of the boost switch T0 and the ground line. One end (positive side) of the capacitor C0 is connected to a connection point between the inductor L0 and the boost switch T0 via the diode D0, and the other end (negative side) of the capacitor C0 is a connection point between the boost switch T0 and the resistor R0. It is connected to the.

  In such a booster circuit 33, when the booster switch T0 is turned on / off, a flyback voltage (back electromotive voltage) higher than the battery voltage VB is generated at the connection point between the inductor L0 and the booster switch T0. The capacitor C0 is charged through the diode D0 by the flyback voltage. For this reason, the capacitor C0 is charged with a voltage higher than the battery voltage VB.

  Then, the charging control circuit 35 turns on / off the boost switch T0. At this time, the voltage on the positive side of the capacitor C0 (hereinafter referred to as capacitor voltage) VC is monitored and the charging current of the capacitor C0 is changed to the resistance R0. The boost switch T0 is turned on / off so that the capacitor C0 is charged in an efficient cycle. Further, when the capacitor voltage VC reaches a preset target voltage (> VB), the charging control circuit 35 keeps the boost switch T0 off and stops charging the capacitor C0. For this reason, the capacitor C0 is charged so that the capacitor voltage VC, which is the charging voltage thereof, becomes the target voltage.

  Still further, the fuel injection control device 31 includes a discharge switch T12 that is a switching element that connects the positive electrode side of the capacitor C0 to the terminal CM, an energy source in which the anode is connected to the terminal INJ, and the cathode is connected to the positive electrode side of the capacitor C0. A recovery control diode D13, a cylinder selection switch T10, a constant current switch T11, and a discharge switch T12 are controlled to control a current flowing through the coil 41a, and a microcomputer (microcomputer) 39 is provided. Yes.

  The microcomputer 39 includes a CPU 61 that executes a program, a ROM 62 that stores programs, fixed data, and the like, and a RAM 63 that stores calculation results and the like by the CPU 61.

  The microcomputer 39 generates an injection command signal for each cylinder based on engine operation information detected by various sensors such as the engine speed Ne, the accelerator opening ACC, and the engine water temperature THW, and the drive control circuit 37. Output to. The injection command signal means that the coil 41a of the solenoid valve 41 is energized (that is, the solenoid valve 41 is opened) only while the level of the signal is high. For this reason, the microcomputer 39 sets an energization period to the coil 41a of the solenoid valve 41 for each cylinder based on the engine operation information, and sets the injection command signal of the corresponding cylinder to high only during the energization period. It can be said.

Next, the relationship between the current that the fuel injection control device 31 passes through the coil 41a of the electromagnetic valve 41 (that is, the driving current of the electromagnetic valve 41) and the operating state of the electromagnetic valve 41 will be described.
As shown in the first and second stages in FIG. 2, the fuel injection control device 31 starts from the capacitor C0 to the coil at the initial stage of the lift period (lifting period) in which the valve body of the electromagnetic valve 41 is lifted to the valve opening position. By discharging to 41a, a larger peak current is passed through the coil 41a than during other periods. During the lift period, after the current flowing through the coil 41a (hereinafter referred to as the coil current) reaches the target maximum value Ip of the peak current, the solenoid valve 41 is kept open in order to realize more reliable valve opening. A pickup current, which is a constant current for generating an electromagnetic force larger than the minimum necessary electromagnetic force, is caused to flow through the coil 41a using the battery voltage VB.

  The fuel injection control device 31 then holds a hold current (<pickup) that is a constant current for generating an electromagnetic force that is at least required for holding the valve open during the valve opening holding period after the lift period ends. Current) is caused to flow through the coil 41a using the battery voltage VB.

  Further, when stopping fuel injection from the electromagnetic valve 41, the fuel injection control device 31 stops supplying current to the coil 41 a and closes the electromagnetic valve 41. A period from when the current supply to the coil 41a is stopped until the solenoid valve 41 is closed is a valve closing period.

  Next, the operation of the drive control circuit 37 will be described with reference to FIGS. Here, the solenoid valve 41 of the nth cylinder #n will be described, but the same applies to the solenoid valves 41 of other cylinders. Further, before the start of fuel injection, the capacitor voltage VC is the target voltage.

  As shown in FIG. 2, when the injection command signal of the nth cylinder #n from the microcomputer 39 to the drive control circuit 37 goes from low to high, the drive control circuit 37 selects the cylinder selection switch corresponding to the nth cylinder #n. Turn on T10. Further, the drive control circuit 37 performs a peak current supply process, which will be described later, to turn on / off the discharge switch T12 with a constant period Ts as illustrated in FIG. 3, for example, and at least turn off the discharge switch T12. If so, the constant current switch T11 is turned on to supply the battery voltage VB to the terminal CM. In this embodiment, as shown in FIGS. 2 and 3, the constant current switch T11 is kept on during the period when the discharge switch T12 is turned on / off. You may make it turn on / off in the opposite state to on / off of T12.

  Then, when the discharge switch T12 is turned on, the capacitor C0 is discharged to the coil 41a. That is, a current flows through a path of “capacitor C0 → discharge switch T12 → coil 41a → cylinder selection switch T10 → resistor R10 → ground line”. During such discharge of the capacitor C0, the wraparound from the terminal CM side to the power supply line Lp side, which becomes a high potential, is prevented by the diode D11. For this reason, there is no problem even if the constant current switch T11 is kept on. Further, when the discharge switch T12 is on, even if the constant current switch T11 is on, the capacitor voltage VC is higher than the battery voltage VB, so that current flows from the capacitor C0 to the coil 41a.

  On the other hand, when the discharge switch T12 is off, a current flows from the battery voltage VB (power supply line Lp) to the coil 41a through the constant current switch T11. That is, a current flows through a path of “power supply line Lp → constant current switch T11 → diode D11 → coil 41a → cylinder selection switch T10 → resistor R10 → ground line”.

  For this reason, the coil current increases as shown by a solid line in FIG. The coil current increases with a slope (Aon) corresponding to the capacitor voltage VC during the ON period of the discharge switch T12, and increases with a slope (Aoff) according to the battery voltage VB during the OFF period of the discharge switch T12.

  In addition, the drive control circuit 37 has passed the target time Tp of the period during which the peak current is supplied to the coil 41a (peak current period) from the start of driving of the electromagnetic valve 41 (in other words, the start of energization to the coil 41a). When this occurs, the discharge switch T12 is turned on / off so that the coil current reaches the target maximum value Ip of the peak current. This will be described later.

  Then, when the drive control circuit 37 detects the coil current based on the voltage generated in the resistor R10 and determines that the coil current has reached the target maximum value Ip, the drive control circuit 37 ends the on / off control of the discharge switch T12, and turns on the discharge switch T12. While keeping it off, the constant current switch T11 is also turned off. At this time, the target time Tp has elapsed from the start of driving of the solenoid valve 41.

  In this embodiment, the period from the start of driving of the solenoid valve 41 until the coil current reaches the target maximum value Ip is also the period from the start of driving of the solenoid valve 41 until the target time Tp elapses. This is a peak current period for supplying a peak current to the coil 41a. In FIG. 3, the waveform of the dotted line is a comparative example, and is the waveform of the coil current when the discharge switch T12 is kept on until the coil current reaches the target maximum value Ip.

  Then, after the coil current reaches the target maximum value Ip, the drive control circuit 37 starts when the fixed time Tf that is the length of the lift period elapses from the start of driving of the solenoid valve 41 (that is, the end of the lift period). The constant current switch T11 is turned on / off so that the coil current detected by the voltage generated in the resistor R10 becomes a constant pickup current smaller than the target maximum value Ip.

  More specifically, the drive control circuit 37 performs the constant current control for causing the pickup current to flow through the coil 41a as follows: “When the coil current falls below the lower threshold value puL of the pickup current control, When the current exceeds the upper threshold value puH of the pickup current control, the control is performed to turn off the constant current switch T11. The relationship between the lower threshold value puL, the upper threshold value puH, and the target maximum value Ip is “puL <puH <Ip”.

  Therefore, when the coil current decreases from the target maximum value Ip and falls below the lower threshold value puL, thereafter, the constant current switch T11 is repeatedly turned on / off, and the average value of the coil current becomes lower than the upper threshold value puH. The pickup current is controlled between the side threshold value puL.

  In such a constant current control, when the constant current switch T11 is turned on, a current flows from the battery voltage VB (power supply line Lp) to the coil 41a in the same manner as when the discharge switch T12 is turned off during the peak current period. Further, when the constant current switch T11 is turned off, a current flows (circulates) through the coil 41a from the ground line side through the diode D12.

  Further, the drive control circuit 37 picks up the coil current detected by the voltage generated in the resistor R10 after the fixed time Tf has elapsed from the start of driving of the solenoid valve 41 (that is, after the lift period has ended). On / off control of the constant current switch T11 is performed so that a constant hold current smaller than the current is obtained.

  More specifically, the drive control circuit 37 performs the constant current control for causing the hold current to flow through the coil 41a as follows: “When the coil current falls below the lower threshold hdL of the hold current control, the constant current switch T11 is turned on. When the current becomes equal to or higher than the upper threshold hdH of the hold current control, the constant current switch T11 is turned off. The lower threshold hdL is smaller than the lower threshold puL of the pickup current control, and the upper threshold hdH is also smaller than the upper threshold puH of the pickup current control.

For this reason, after the lift period ends, the average value of the coil current is controlled to a hold current (<pickup current) between the upper threshold hdH and the lower threshold hdL.
Thereafter, when the injection command signal for the nth cylinder #n from the microcomputer 39 changes from high to low, the drive control circuit 37 turns off the cylinder selection switch T10 corresponding to the nth cylinder #n, and the constant current switch T11. The on / off control (that is, constant current control) is terminated, and the constant current switch T11 is also kept off. Then, energization of the coil 41a is stopped, the electromagnetic valve 41 is closed, and fuel injection by the electromagnetic valve 41 is terminated.

  A period from the end of the lift period until the injection command signal becomes low is a valve opening holding period in which a hold current flows through the coil 41a. When the high time of the injection command signal is shorter than the predetermined time Tf, the valve opening holding period disappears, and the energization to the coil 41a is stopped during the pickup current supply period.

  When the injection command signal becomes low and the cylinder selection switch T10 and the constant current switch T11 are turned off, flyback energy is generated in the coil 41a. The flyback energy is a diode D13 that forms an energy recovery path. And is recovered in the form of current to the capacitor C0.

Next, the reason why the discharge switch T12 is turned on / off during the peak current period will be described.
As a method for supplying the peak current to the coil 41a of the electromagnetic valve 41, it is assumed that a method is adopted in which the discharge switch T12 is kept on until the coil current reaches the target maximum value Ip from the start of driving of the electromagnetic valve 41. This method is called a continuous discharge method.

In the case of the continuous discharge method, the peak current period until the coil current reaches the target maximum value Ip depends on the capacitor voltage VC and becomes shorter as the capacitor voltage VC becomes higher.
Here, in FIG. 4, the solid line indicates the case where the peak current period is the optimum length, the one-dot chain line indicates the case where the peak current period is longer than the optimum length, and the two-dot chain line indicates that the peak current period is greater than the optimum length. Also shows a short case.

  Further, in the uppermost stage of FIG. 4, the waveform indicated by the dotted line indicates that the peak current indicated by the two-dot chain line is passed through the coil 41a of the solenoid valve 41 in the second stage of FIG. In this case, the actual change in lift amount is as indicated by a two-dot chain line in the uppermost stage of FIG.

  That is, if the peak current period is too short (that is, shorter than the optimum length), the moving speed of the valve body of the electromagnetic valve 41 does not increase as expected. This is because it is difficult to move a heavy object at once. When the peak current period is too short, the magnetic force generated by the peak current is not sufficiently used for the lift movement of the valve body, and is converted into heat inside the electromagnetic valve 41. The loss of electrical energy will increase. This loss is a loss at the initial stage of driving.

  For this reason, when the peak current period becomes too short, as shown in the lowermost stage of FIG. 4, in addition to the energy used to lift the valve body of the solenoid valve 41, the capacitor C0 has a loss amount at the initial stage of driving. As a result, it is necessary to store extra energy, and as a result, a capacitor having a large capacitance is required as the capacitor C0.

  Further, in the solenoid valve 41 of the present embodiment, the optimum value of the capacitor voltage VC when driving by the continuous discharge method (that is, the capacitor voltage VC having the optimum length of the peak current period by the continuous discharge method) is, for example, 50V. . However, in the fuel injection control device 31 of the present embodiment, the actual capacitor voltage VC is controlled to a target voltage (for example, 60 V) higher than the optimum value (50 V) when the solenoid valve 41 is driven by the continuous discharge method. .

  This is because in the fuel injection control device 31 of the present embodiment, the electric energy of the capacitor C0 is also used to drive an electric load different from the electromagnetic valve 41. The other electric load is, for example, a solenoid valve for other applications, and more specifically, for example, for controlling the fuel discharge amount of a fuel pump that feeds the fuel in the fuel tank to a common rail with a high pressure. The solenoid valve (hereinafter referred to as a pump solenoid valve).

  In FIG. 1, a switch denoted by reference sign “T22” is a switch that discharges from the capacitor C0 to the coil 51a of the pump solenoid valve 51 when turned on. The coil 51a of the pump solenoid valve 51 is supplied with a peak current by a continuous discharge method, and the optimum capacitor voltage VC for driving the pump solenoid valve 51 is, for example, 60V. is there.

For this reason, if peak current is supplied also to the coil 41a of the solenoid valve 41 by the continuous discharge method, the peak current period becomes too short and the loss at the initial stage of driving becomes large.
Therefore, in the fuel injection control device 31 of the present embodiment, the peak current period is prevented from becoming too short by extending the discharge switch T12 during the peak current period of the solenoid valve 41, and extended. Prevents the loss at the initial stage of driving from becoming large.

Next, the contents of processing performed by each of the microcomputer 39 and the drive control circuit 37 in order to supply the peak current to the coil 41a of the electromagnetic valve 41 will be described with reference to FIGS.
When the microcomputer 39 is activated as the fuel injection control device 31 is turned on, the microcomputer 39 performs the initial setting process of FIG. 5 before starting the control of the electromagnetic valve 41 (before starting the output of the injection command signal).

As shown in FIG. 5, when starting the initial setting process, the microcomputer 39 first determines the type of the solenoid valve 41 to be driven in S110.
For example, an identification signal capable of distinguishing the type of the solenoid valve 41 connected to the fuel injection control device 31 is input to the microcomputer 39 by a jumper wire or a dip switch mounted on the printed wiring board together with the microcomputer 39. In this case, the microcomputer 39 can determine the type of the electromagnetic valve 41 by reading the identification signal. Further, for example, if the microcomputer 39 and the electromagnetic valve 41 can communicate with each other by wire or wireless, the microcomputer 39 acquires the model number information indicating the type of the electromagnetic valve 41 from the electromagnetic valve 41 by communication. Thus, the type of the electromagnetic valve 41 can be determined.

Next, in S120, the microcomputer 39 determines a control parameter according to the type of the electromagnetic valve 41 determined in S110.
The control parameter is information used to supply a peak current to the coil 41a of the electromagnetic valve 41. The control parameters include a target maximum value Ip of the peak current, a target time Tp of the peak current period, a cycle Ts for turning on / off the discharge switch T12, and a control start state of the discharge switch T12. The control start state is information indicating whether the on / off control of the discharge switch T12 is started on or off. The cycle Ts is set to a time “1 / N” of the target time Tp (N is an integer of 1 or more).

  Such control parameters are stored in the ROM 62 for each of a plurality of types of the solenoid valves 41, for example. In S120, the microcomputer 39 selects a control parameter corresponding to the type of the solenoid valve 41 determined in S110 from the plurality of sets of control parameters stored in the ROM 62, and the selected control parameter is changed to the electromagnetic parameter. It is determined as a control parameter used for controlling the valve 41. For this reason, the control parameter used for control of the solenoid valve 41 is changed according to the type of the solenoid valve 41.

Further, in the next S130, the microcomputer 39 selects a battery voltage versus current gradient table according to the type of the solenoid valve 41 determined in S110.
The battery voltage vs. current slope table shows the slope of the coil current when the battery voltage VB and the battery voltage VB are applied to the upstream side of the coil 41a (the rate of change of the coil current with time, and the increment per unit time). Is a data table showing a plurality of battery voltages VB. For this reason, the battery voltage versus current slope table indicates that the slope of the coil current (hereinafter also referred to as current slope) increases as the battery voltage VB increases. Moreover, the battery voltage versus current gradient table is stored in the ROM 62 for each of a plurality of types of the electromagnetic valves 41, for example. In S130, the microcomputer 39 selects a battery voltage versus current slope table corresponding to the type of the solenoid valve 41 determined in S110 from among a plurality of battery voltage versus current slope tables stored in the ROM 62.

Next, in S140, the microcomputer 39 detects the actual battery voltage VB.
Although not shown in FIG. 1, for example, the battery voltage VB is divided by a resistor and input to the microcomputer 39. The microcomputer 39 performs A / D conversion on the input voltage-divided voltage by an internal A / D converter, and detects the battery voltage VB from the A / D conversion value.

  Next, in S150, the microcomputer 39 determines the slope of the coil current during the ON period of the discharge switch T12 (hereinafter referred to as ON current slope) Aon and the slope of the coil current during the OFF period of the discharge switch T12 (hereinafter referred to as OFF current). Aoff) (referred to as inclination) is determined.

  The on-current gradient Aon is a current gradient when the capacitor voltage VC is applied to the upstream side of the coil 41a, and depends on the capacitor voltage VC and the type of the electromagnetic valve 41 (specifically, the electrical characteristics of the coil 41a). The capacitor voltage VC is controlled to a known target voltage (the above-described 60 V in this embodiment). For this reason, for example, the ROM 62 stores an on-current gradient Aon for each of a plurality of types of the solenoid valve 41. In S150, the microcomputer 39 selects an on-current gradient Aon corresponding to the type of the solenoid valve 41 determined in S110 from among a plurality of on-current gradients Aon stored in the ROM 62. The selected on-current gradient Aon becomes the determined value of the on-current gradient Aon.

  The off-current gradient Aoff is a current gradient when the battery voltage VB is applied to the upstream side of the coil 41a, and depends on the battery voltage VB and the type of the electromagnetic valve 41. Therefore, in S150, the microcomputer 39 calculates a current gradient corresponding to the battery voltage VB detected in S140 from the battery voltage versus current gradient table selected according to the type of the solenoid valve 41 in S130. The calculated current gradient becomes a determined value of the off-current gradient Aoff.

  As a modification, the on-current gradient Aon may be determined based on the actual capacitor voltage VC as in the off-current gradient Aoff. In that case, a capacitor voltage versus current slope table similar to the battery voltage versus current slope table is created for each type of solenoid valve 41 and stored in the ROM 62. The capacitor voltage vs. current slope table is a data table showing the relationship between the capacitor voltage VC and the slope of the coil current when the capacitor voltage VC is applied to the upstream side of the coil 41a for a plurality of capacitor voltages VC. is there. In S130, the microcomputer 39 selects the capacitor voltage vs. current slope table from those stored in the ROM 62 according to the type of the electromagnetic valve 41 determined in S110. The capacitor voltage VC is also detected by the same method as the battery voltage VB. In S150, the current gradient corresponding to the capacitor voltage VC detected in S140 is calculated from the capacitor voltage versus current gradient table selected in S130, and the calculation is performed. The determined current gradient may be used as the determined value of the on-current gradient Aon.

  Next, in S160, the microcomputer 39 uses the target maximum value Ip and the target time Tp determined in S120 and the on-current gradient Aon and the off-current gradient Aoff determined in S150 to achieve the target time from the start of driving of the solenoid valve 41. A drive duty ratio (that is, duty ratio of on / off control) D of the discharge switch T12 is determined so that the coil current becomes the target maximum value Ip when Tp has elapsed.

  Specifically, the drive duty ratio D is a ratio of the on time Ton to the period Ts (= Ton / Ts). Then, in S160, the microcomputer 39 calculates a drive duty ratio D that satisfies the following formula 1. If the sum of the on time Ton at the target time Tp is ΣTon, the drive duty ratio D is also the ratio of ΣTon to the target time Tp.

{Aon × Tp × D} + {Aoff × Tp (1−D)} = Ip Equation 1
Next, in S170, the microcomputer 39 determines the drive duty ratio D determined in S160, the cycle Ts and the control start state in the control parameters determined in S120, and the target maximum value Ip in the control parameters determined in S120. Alternatively, the target time Tp is commanded to the drive control circuit 37 as control information. Thereafter, the initial setting process is terminated. As shown in FIG. 1, a signal line 65 for providing control information from the microcomputer 39 to the drive control circuit 37 is disposed between the microcomputer 39 and the drive control circuit 37.

Then, the drive control circuit 37 performs a peak current supply process shown in FIG.
As shown in FIG. 6, when the drive control circuit 37 detects that the injection command signal of the nth cylinder #n has changed from low to high (S210: YES), the cylinder selection switch corresponding to the nth cylinder #n T10 is turned on (S220). Further, the drive control circuit 37 turns on the constant current switch T11 (S230) and starts on / off control of the discharge switch T12 (S240).

  The on / off control of the discharge switch T12 is performed according to the drive duty ratio D, the cycle Ts, and the control start state instructed as control information from the microcomputer 39. That is, the drive control circuit 37 turns on / off the discharge switch T12 at the commanded cycle Ts and the drive duty ratio D, and the drive state of the discharge switch T12 at the start of each cycle Ts is controlled by the commanded control. Set to the start state. For this reason, if the commanded control start state is “on”, the discharge switch T12 repeats {turns on for “Ts × D” and then off for “Ts × (1-D)”} as one cycle. On / off, conversely, if the commanded control start state is “off”, the discharge switch T12 is turned off by “Ts × (1-D)” and then on by “Ts × D”}. Is repeatedly turned on / off in one cycle.

  The drive control circuit 37 compares the detected value of the coil current with the target maximum value Ip commanded from the microcomputer 39, and turns on / off the discharge switch T12 until it is determined that the coil current has reached the target maximum value Ip. The control and the constant current switch T11 are kept on (S250: NO).

  When the drive control circuit 37 determines that the coil current has reached the target maximum value Ip (S250: YES), the drive switch circuit 37 turns off the discharge switch T12 and the constant current switch T11 (S260). It shifts to the state where constant current control for flowing is performed.

The determination example of S250 is an example in which the target maximum value Ip is commanded from the target maximum value Ip and the target time Tp to the drive control circuit 37 from the microcomputer 39.
On the other hand, when the target time Tp is commanded from the microcomputer 39 to the drive control circuit 37, the drive control circuit 37 determines whether or not the target time Tp has elapsed since the start of driving of the solenoid valve 41 in S250. If it is determined that the target time Tp has elapsed (S250: YES), the discharge switch T12 and the constant current switch T11 can be turned off (S260). In the present embodiment, the discharge switch T12 is turned on / off so that the coil current becomes the target maximum value Ip when the target time Tp has elapsed since the start of driving of the solenoid valve 41. This is because the timing at which the time Tp elapses is the same as the timing at which the coil current reaches the target maximum value Ip.

  In the fuel injection control device 31 as described above, the microcomputer 39 and the drive control circuit 37 allow the coil current to reach the target maximum value Ip of the peak current when the target time Tp has elapsed from the start of driving of the solenoid valve 41. Then, the discharge switch T12 is turned on / off. For this reason, although the capacitor voltage VC is controlled to a voltage higher than the optimum value when the electromagnetic valve 41 is driven by the continuous discharge method, the coil current becomes the target maximum value Ip from the start of driving of the electromagnetic valve 41. The peak current period until becomes can be the target time Tp. Therefore, loss of electric energy (loss at the initial stage of driving) due to the peak current period being too short can be prevented, and energy efficiency can be improved.

  Further, in the peak current period, the constant current switch T11 may be kept off. However, in the present embodiment, since the constant current switch T11 is turned on, at least when the discharge switch T12 is turned off, The battery voltage VB is supplied to the upstream side (terminal CM) of the coil 41a. For this reason, as shown by a solid line in FIG. 3, for example, even when the discharge switch T12 is off during the peak current period, the coil current can be supplied from the battery voltage VB to the coil 41a to increase the coil current. Therefore, it is easy to ensure a current increase rate necessary for opening the solenoid valve 41 quickly.

  Further, since the battery voltage VB is supplied to the upstream side of the coil 41a by turning on the constant current switch T11 during the peak current period, it is not necessary to separately provide other means for supplying the battery voltage VB. As another means, for example, a switch (switching element) provided in parallel with the constant current switch T11 can be considered, but such a switch is not necessary.

  Further, the microcomputer 39 detects the battery voltage VB (S140), calculates an off-current gradient Aoff corresponding to the detected battery voltage VB (S150), and determines the drive duty ratio D using the off-current gradient Aoff. (S160). Therefore, the drive duty ratio D is changed according to the detected battery voltage VB. Specifically, the drive duty ratio D is set to a larger value as the battery voltage VB is lower.

  Therefore, even if the battery voltage VB varies, the length of the peak current period can be set to the target time Tp. For example, when the battery voltage VB is reduced from the usual 14V to 10V due to the operation of an electric load having a large current consumption such as an air conditioner device, the off-current gradient Aoff is reduced, but the drive duty ratio D is correspondingly reduced. By increasing the length, the length of the peak current period can be kept constant.

  Further, since the microcomputer 39 changes the target time Tp and the target maximum value Ip according to the type of the electromagnetic valve 41 (S110, S120), the peak current period and the peak current of the optimum length for the electromagnetic valve 41 are changed. The maximum value can be realized.

As a modification, one or both of the target time Tp and the target maximum value Ip is not changed depending on the type of the electromagnetic valve 41, but may be a fixed value.
Further, the microcomputer 39 also changes the cycle Ts for turning on / off the discharge switch T12 according to the type of the electromagnetic valve 41 (S110, S120), thereby realizing a coil current waveform suitable for the electromagnetic valve 41, The electromagnetic valve 41 can be driven appropriately.

  For example, when the electromagnetic valve 41 to be driven has a relatively small load at the initial stage of lift of the valve body (at the start of lift), the period Ts for realizing the waveform of the coil current indicated by the solid line in FIG. However, by adopting a large period Ts so that the waveform of the coil current becomes, for example, a waveform as shown by a one-dot chain line in FIG. 3, the valve body can be pulled up at once. 3 is a waveform of the coil current when the period Ts is set to the same value as the target time Tp. In the waveform of the alternate long and short dash line, the initial slope is the on-current slope Aon. The later gentle slope is the off-current slope Aoff.

  Further, the microcomputer 39 changes the control start state of whether the on / off control of the discharge switch T12 is started according to the type of the electromagnetic valve 41 (S110, S120). Also by this, the waveform of the coil current suitable for the electromagnetic valve 41 can be realized, and the electromagnetic valve 41 can be driven appropriately. The method of switching the control start state is advantageous particularly when the period Ts is set to be long.

  For example, when the solenoid valve 41 to be driven has a relatively large load at the initial stage of lifting the valve body, the control start state is set to “off”, and the initial increase slope of the coil current is turned off. The current gradient Aoff may be set. More specifically, by setting the control start state to “off” so that the waveform of the coil current becomes, for example, a waveform as shown by a two-dot chain line in FIG. 3, the battery voltage is first applied to the coil 41 a. It is possible to make it easier to move the valve body by flowing a current gently from VB, and then increase the pulling speed of the valve body by flowing a current from the capacitor C0 to the coil 41a (that is, by turning on the discharge switch T12). . In addition, the waveform of the two-dot chain line in FIG. 3 is also the waveform of the coil current when the cycle Ts is set to the same value as the target time Tp, similarly to the waveform of the one-dot chain line. , The first slope is the off-current slope Aoff, and the later steep slope is the on-current slope Aon.

  Further, for example, when the electromagnetic valve 41 to be driven has a relatively small load at the initial stage of pulling up the valve body, the control start state is set to “on”, and the initial increase slope of the coil current is The on-current gradient Aon may be set. More specifically, by setting the control start state to “on” so that the waveform of the coil current becomes, for example, a waveform as shown by a one-dot chain line in FIG. The valve body is pulled up at a stroke by flowing an electric current, and then the bounce of the valve body at the pulling stop position is suppressed by reducing the moving speed of the valve body so that the current flows from the battery voltage VB to the coil 41a. Can be realized.

  As mentioned above, although one Embodiment of this invention was described, this invention is not limited to such Embodiment at all, Of course, in the range which does not deviate from the summary of this invention, it can implement in a various aspect. .

  For example, the microcomputer 39 may perform what the drive control circuit 37 does. The electromagnetic valve 41 to be driven is not limited to an injector, and may be an electromagnetic valve of a fuel pump, for example. The engine provided with the electromagnetic valve 41 to be driven may be a gasoline engine.

  In addition, within the scope of the contents described in the claims, it is of course possible to perform a modification that changes any combination of the configurations and processes of the above-described embodiments, a modification that deletes a part, or the like. is there.

  For example, a configuration in which the above-described control parameter is not changed according to the type of the electromagnetic valve 41 may be employed. In that case, as the control parameter, a value suitable for the electromagnetic valve 41 to be driven may be stored in the ROM 62 or the like in advance.

  33 ... Booster circuit, 37 ... Drive control circuit, 39 ... Microcomputer, 41 ... Solenoid valve, 41a ... Coil, T11 ... Constant current switch, T12 ... Discharge switch, C0 ... Capacitor, CM ... Terminal, Lp ... Power line, VB ... Battery voltage

Claims (7)

Charging means (33) for charging the capacitor so that the charging voltage of the capacitor (C0) becomes a predetermined voltage higher than the power supply voltage (VB);
A discharge switch (T12) for connecting the capacitor to the upstream side (CM) of the coil in the energization path for flowing current to the coil (41a) of the electromagnetic valve (41);
By turning on the discharge switch and discharging the coil from the capacitor to the coil, peak current supply means (37, 39, S110 to S170, S230-S250),
In a solenoid valve drive device comprising:
The peak current supply means turns on / off the discharge switch so that a current flowing through the coil reaches a target maximum value of the peak current when a target time has elapsed from the start of driving of the solenoid valve. ,
A solenoid valve driving device characterized by the above. In the electromagnetic valve drive device according to claim 1,
The peak current supply means is at least when the discharge switch is turned off during the peak current period from when the driving starts until the current flowing through the coil reaches the target maximum value. Comprising power supply means (S230) for supplying the power supply voltage upstream;
A solenoid valve driving device characterized by the above. In the solenoid valve drive device according to claim 2,
A constant current switch (T11) that is turned on / off between the power supply line (Lp) to which the power supply voltage is supplied and the upstream side of the coil in the energization path to allow a constant current to flow through the coil. Is provided,
The power supply means supplies the power supply voltage upstream of the coil in the energization path by turning on the constant current switch;
A solenoid valve driving device characterized by the above. In the electromagnetic valve drive device according to claim 2 or claim 3,
The peak current supply means includes voltage detection means (S140) for detecting the power supply voltage, and changes a duty ratio for turning on / off the discharge switch according to the power supply voltage detected by the voltage detection means. (S150, S160),
A solenoid valve driving device characterized by the above. In the electromagnetic valve drive device according to any one of claims 2 to 4,
The peak current supply means changes whether the on / off control of the discharge switch is started according to the type of the solenoid valve (S110, S120),
A solenoid valve driving device characterized by the above. In the electromagnetic valve drive device according to any one of claims 1 to 5,
The peak current supply means changes at least one of the target time and the target maximum value according to the type of the solenoid valve (S110, S120),
A solenoid valve driving device characterized by the above. In the solenoid valve drive device according to any one of claims 1 to 6,
The peak current supply means changes a cycle for turning on / off the discharge switch according to the type of the solenoid valve (S110, S120),
A solenoid valve driving device characterized by the above.

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